The present invention relates to a structure of semiconductor device and a method of manufacture thereof.
To increase the capacity of data communication, it is desired that a variety of kinds of circuit components to be integrated to develop highly integrated small devices with sophisticated functions. For this end, a technology is required that permits free integration of semiconductor devices of different kinds. A technology currently in wide use for making a semiconductor layered structure that constitutes a fundamental structure of the semiconductor device elements is an epitaxial growth. The drawbacks of the epitaxial growth technology include the difficulty in growing on a substrate a layer whose lattice constant and thermal expansion coefficient are different from those of the substrate and the fact that the crystallographic orientation of the grown layer is limited to the same crystallographic orientation of the substrate. Hence, it is difficult to integrate two semiconductor devices if the physical property constants of their constituent materials, such as lattice constant and thermal expansion cosfficient, are different from each other. Moreover, when the crystallographic orientations of the constituent materials differ from each other, the semiconductor devices cannot be integrated.
To deal with these problems, a method has been proposed in recent years, which directly bonds two semiconductors at elevated temperatures and under some pressures without using adhesives or interposing an insulating film. As described in the Applied Physics Letters, 58, 1961 (1991), this method is reported to be able to unite semiconductors, such as InP and GaAs, having greatly different physical properties like lattice constant and to form a semiconductor device with good characteristics. The InP and GaAs directly bonded together, however, have the same crystallographic orientations, and there are no reports on a case where two kinds of semiconductors are bonded together with different crystallographic orientations.
The Electronics Letters, 29 1942 (1993), and Japan Patent Publication No. 38536/1994 describe a method of directly bonding semiconductors with different crystallographic orientations to form a single device. However, the two semiconductors bonded together are combinations of GaAs and GaAs, and of InP and InP in each documents, that is, the bonding combination is limited to the same kind of semiconductors. It is also noted that in either case of direct bonding, the device produced by bonding two semiconductors is single devices and that no method is presented for manufacturing integrated devices.